The present invention relates to a semiconductor device represented by an LSI, and more particularly to a connection between a Cu film for wiring and an Al film for a pad.
FIG. 10 is a sectional view showing a structure of a conventional semiconductor device having the Cu film for wiring and the Al film for the pad.
In an example shown in FIG. 10 there is shown a state in which a second layer region (comprising an interlayer insulating film 21, a barrier layer 22 and a Cu film 23 for wiring) is formed on a first layer region (an interlayer insulating film 11, a barrier layer 12 and a metal film 13 for wiring), and a third layer region (a silicon nitride film 31, an upper layer insulating film 32, a barrier layer 33 and an Al film 34 for a pad) are formed on the second layer region.
As shown in FIG. 10, a barrier layer 33 is provided between the Cu film 23 for wiring and the Al film 34 for the pad. This barrier layer 33 is provided for preventing a mutual diffusion between the Cu film 23 and the Al film 34. For a barrier metal of the barrier layer 33, a refractory metal nitride such as TaN, NbN, TiN, WN, VN or the like is used.
However, in the prior art, there is a problem in that when the Al film 34 is formed by the sputtering method or the like, Al contained in the Al film 34 and the N contained in the barrier layer 33 are allowed to react with each other to form AlNx which is an insulator so that the resistance (particularly via resistance) is raised with AlNx. Furthermore, there is also a problem in that since adherence between the silicon oxide film used for the upper layer insulating film 32 and the refractory metal nitride film used for the barrier layer 33 is poor, oxide invades from a gap between the silicon oxide film and the refractory metal nitride film with the result that the Cu film 23 is oxidized.
In this manner, in order to prevent mutual diffusion between the Cu film for wiring and the Al film for the pad, a refractory metal nitride film is provided as a barrier layer between the Cu film and the Al film. However, there is a problem in that a resistance is raised because of AlNx formed with a reaction between Al and N. There is also a problem in that the Cu film is oxidized because of poor adherence between the upper layer insulating film and the barrier layer. Thus, this leads to the deterioration of characteristic and reliability of the semiconductor device.